1. Field of the Invention
The present invention relates to an exposure method and apparatus which draw a pattern on a substrate such as a wafer or glass plate using a charged particle beam such as an electron beam or an ion beam.
2. Description of the Related Art
Electron beam exposure apparatuses are roughly classified into apparatuses for scanning a point beam on a wafer to draw a pattern and apparatuses for shaping an electron beam into a desired shape using a mask and transferring the mask pattern on a wafer. In both apparatuses, to expose a pattern on the entire wafer surface, the stage on which the wafer is placed must be moved to move the wafer relative to the electron beam.
In such a conventional apparatus, however, as the stage moves, the position of the electron beam changes accordingly, and the pattern cannot be drawn or transferred to the desired position on the wafer. This is probably because the electromagnetic field near the electron beam varies during movement of the stage. Especially, when a magnetic material is used for the stage which moves, the position of the electron beam conspicuously changes during movement of the stage.
Particularly, since the position of the electron beam changes during movement of the stage, the imaging characteristics (e.g., the focus position or astigmatic amount) of the electron beam may vary, and the pattern cannot be drawn or transferred to the desired position on the wafer. This is probably because the electromagnetic field near the electron beam varies during movement of the stage. Especially, when a magnetic material is used for the stage which moves, the imaging characteristics (e.g., the focus position or astigmatic amount) of the electron beam conspicuously vary during movement of the stage.